This invention relates to self-contained devices for maintaining pressure in rotating elements, such as vehicle tyres.
Devices for maintaining vehicle tyre pressure are disclosed in U.S. Pat. No. 7,013,931 and in PCT Application No. PCT/IB2013/054732, (published as WO 2014/009822). The devices are attached to vehicle wheels and each includes a hanging, stationary counterweight, while the remainder of the device normally rotates with the wheel. When a tyre on the vehicle wheel loses pressure, a part of the device becomes connected to the counterweight by a pneumatically operated friction clutch, so that it becomes stationary. Relative motion between the part that is stationary and the remainder of the device is used to drive a pump that pressurises the tyre to the desired pressure.
The present invention seeks to provide a simple and cost-effective improvement on such prior devices.